The present invention relates to a suction box for the use in a section of a machine for the manufacturing a fiber web, for instance a paper web, and particularly to regulating the size of the suction entry toward the belt carrying the fiber web to which suction is being applied.
A suction box of a similar type is disclosed in Federal Republic of Germany Patent 1937740.
In a paper manufacturing machine, such a suction box is used in the forming section of the machine for removing water from a fiber suspension for a paper web which is being formed either on a wire belt or between two wire belts called wires. The wire or wires travel over the inlet side of the suction box, together with the fiber web or the web of paper from which the water is to be removed. The vacuum in the suction box helps to remove water from the fiber or paper web passing over the box. The suction box is not restricted to use in a forming section, but may be used for other sections where suction is to be applied to a moving belt. The belt may be a wire or may be a felt or fabric belt, but is a belt suitable for the respective section of the machine.
The suction box has at least two spaced apart support strips, and typically has more than two support strips, which come into contact with the wire belt, or with one of the two wire belts. There is a suction slot defined between every two support strips. In DE '740, the length of a suction slot, and thus the length of the suction zone, is determined by two sealing strips. In other known constructions, slot fillers are fitted in sealing manner between adjacent support strips on each lateral end of the suction box, i.e. in the regions on both sides of the wire belt. The placement of the fillers determines the length of the respective suction zones in the direction across the wire. If necessary, at least some of the fillers can be shifted transversely to the direction of travel of the wire belt, in order to change the length of the respective suction zones across the wire. Such fillers are generally referred to as format slides.
The above DE '740 is concerned inter alia with the problem of reducing wearing of the wire and on the support strips. This wear is caused by the wire belt or in other cases a felt belt, travelling in direct contact over the support strips of the suction box. In DE '740, this wear is reduced by reducing the distance between the support strips as much as possible. In actual practice, however, at times there is still premature wear of the wire belt, particularly in the regions toward the lateral sides of the wire belt.